When cleansing with washing and rinsing apparatuses it very often occurs that the object to be cleansed must be subjected to cleansing with a chemical detergent during the cleansing procedure. This detergent is usually added to the cleansing liquid, which generally is water, by means of an injector. The detergent thus is admixed with rinsing water, which furthermore may have an increased water pressure, if the washing and rinsing apparatus is a high pressure apparatus. As the addition of the detergent occurs in connection with the rinsing, only a small part of the detergent supplied will actively take part in the dissolving of the dirt. The major part of the detergent is flushed away when the jet of water hits the object to be cleansed. Manual application of the detergent has therefore been resumed, whereby the detergent will have a possibility actively to act upon the layer of dirt.
From U.S. Pat. No. 4,505,431 is earlier known a foam-forming device, wherein water causes injection of a foam-forming fluid in an injector, which is also connected to a source of pressurized air, in such a manner that pressurized air is supplied to an annular slot around the injector diffusor. The quantity of air supplied in relation to the water quantity flowing through is rather small, which means that a foam of high water content is formed, i.e. a foam of rather short duration. The big excess of water in the foam furthermore causes the detergent to be heavily diluted resulting in an inferior cleansing effect.